A relation of lowered cholesterol to increased aggressive behaviors (including suicide) and impaired cognition has been variably demonstrated and remains to be established or excluded with confidence. HMG-CoA reductase inhibitors ("statins") are the most widely used agents and their effects are of special interest. Purpose: To examine the effect of statins on aggressive responding, cognition, and serotonin in individuals with moderate LDL and no identified cardiovascular disease (CVD). Hypothesis: Statin therapy will increase aggressive responding on the PSAP (Point Subtraction Aggression paradigm, a standardized aggression measure that correlates with both violent behavior and serotonin); will reduce measures of cognition (including psychomotor speed and attention); and will change serotonin (gauged by whole blood serotonin), which may be a mediator of effects on behavior and perhaps cognition. Secondarily, it is hypothesized that simvastatin (lipophilic) will exert more potent effects on cognition (and perhaps aggression) than pravastatin (hydrophilic); that serotonin (5HT) changes will related to changes in aggressive responding and perhaps cognition; and that a "susceptible subset" may be defined by baseline characteristics including biochemistry, mood, personality, and extremes of cardiovascular reactivity.